Enterobactersp．SYA2乳糖酶酶学性质研究

采用硫酸铵盐析对Enterobactersp．SYA2乳糖酶进行分级沉淀，研究了该酶的最适作用温度、热稳定性、最适作用pH、pH稳定性及金属离子的影响。结果表明：选取硫酸铵的饱和度30％～85％进行分级沉淀，分级沉淀后得到乳糖酶的比活为45．85U／mg；该酶最适作用温度为40℃～45℃，在35℃和40℃处理时酶活损失不大，在45℃和50℃处理时酶活损失较大，最适作用pH为6．5，pH在6．0－8．5酶活最为稳定，Mg^2＋、Mn^2＋、Na^＋对该酶有一定激活作用，Zn^2＋,Cu^2、Fe^2＋对该酶有不同程度的抑制作用，当酶添加量为1U／mL，乳清水解率3h达50％；而添加量为2U／mL时乳清水解率1h达50％。

Properties of lactase produced by Enterobacter sp.SYA2

The lactase produced by Enterobacter sp. SYA2 was purified by ammonium sulfate precipitation. The optimum temperature, thermostability, optimum pH and pH stability of the lactase were investigated, as well as the effects of metal ions on enzymatic activity. The result showed that the specific activity ofEnterobactersp. SYA2 lactase was 45.85U/mg when the precipitation was performed at 30%-85% saturation with ammonium sulfate. The optimum temperature of the lactase was 40℃--45℃. The lactase was stable at 35℃ and 40℃, but the loss of activity Was obvious at 45℃ and 50℃. The optimum pH of the lactase was 6.5. The lactase was stable at pH 6.0-8.5. The lactase activity could be activated by Mg^2＋, Mn^2＋ and Na^＋, and be inhibited differently by Zn^2＋, Cu^2＋ and Fe^2＋. The hydrolysis rate of lactose in whey was 50% when 1U/ml lactase was used for 3h, or 2U/mL lactase was used for 1h.